1. Field of the Invention
The field of the invention is data processing, or, more specifically, methods, apparatuses, and computer program products for preserving, from resource management adjustment, portions of an overcommitted resource managed by a hypervisor.
2. Description of Related Art
The development of the EDVAC computer system of 1948 is often cited as the beginning of the computer era. Since that time, computer systems have evolved into extremely complicated devices. Today's computers are much more sophisticated than early systems such as the EDVAC. Computer systems typically include a combination of hardware and software components, application programs, operating systems, processors, buses, memory, input/output devices, and so on. As advances in semiconductor processing and computer architecture push the performance of the computer higher and higher, more sophisticated computer software has evolved to take advantage of the higher performance of the hardware, resulting in computer systems today that are much more powerful than just a few years ago.
One area in which computer software has evolved to take advantage of high performance hardware is the set of software tools referred to as hypervisors. A hypervisor is a layer of system software that runs on the computer hardware beneath an operating system layer to allow multiple operating systems to run, unmodified, on a host computer at the same time by providing each operating system with a set of virtual resources. These virtual resources provide each operating system a portion of the actual resources of the computer. Resources, such as a processor, may be implemented as time slices of the total time the resource is available for use. Other resources, such as memory, may be divided among multiple guest operating systems, where each guest is allocated an instance of memory. Using a hypervisor, the distribution of computer resources within a single computer makes the computer appear to function as if it were two or more independent computers.
To ensure maximum utilization of resources, often hypervisors over-commit a resource to guest operating systems. For example, if a hypervisor creates the illusion that there are more instances (or bandwidth) of a resource than actually physically available, that resource is considered to be overcommitted. In an overcommitted resource environment, the hypervisor may balance the demands of the guest operating systems by performing resource management adjustments. In response to a resource management adjustment, the speed and efficiency of a particular guest operating system may be diminished.